Self propelled sewage sludge excavator

ABSTRACT

Apparatus for removing dried sludge from the upper surface of a drying bed in a sewage treatment plant including an excavator which has a plurality of double tined conveyor scoops which travel in an endless path to remove caked sludge from the drying bed and deposit it onto a conveyor. The excavator is positioned for reciprocation above the bed in parallel rows with the double tined scoops enabling excavation in both directions of movement of the excavator along the parallel rows. The trailing edge of the scoops is prevented from cutting into the sand as the scoops commence their upward movement after being charged with the sludge.

United States Patent Martin, Jr. et al.

[4 1 Sept. 5, 1972 [54] SELF PROPELLED SEWAGE SLUDGE EXCAVATOR [7 3]Assignee: R. J. Reynolds Tobacco Company,

Forsyth, N.C.

[22] Filed: June 24,197]

[21] Appl.No.: 156,358

[52] U.S. Cl ..2l4/l7 DB, 37/192 R, 198/77,

198/110, 198/148, 198/152, 210/271, 210/527 [51] Int. Cl ..B65g 65/38[58] Field of Search.....214/17 DB; 37/191 R, 192 R; 210/271, 527',15/1465; 198/77, 110, 148, 152

[56] References Cited UNITED STATES PATENTS 2,801,014 7/1957 Colson..2l4/17 DB 3,473,185 10/1969 Bahr ..214/17DB Primary Examiner-Robert G.Sheridan [57] ABSTRACT Apparatus for removing dried sludge from theupper surface of a drying bed in a sewage treatment plant including anexcavator which has a plurality of double tined conveyor scoops whichtravel in an endless path to remove caked sludge from the drying bed anddeposit it onto a conveyor. The excavator is positioned forreciprocation above the bed in parallel rows with the double tinedscoops enabling excavation in both directions of movement of theexcavator along the parallel rows. The trailing edge of the scoops isprevented from cutting into the sand as the scoops commence their upwardmovement after being charged with the sludge.

10 Claims, 7 Drawing Figures Patented Sept. 5,- 1972 5 Sheets-Sheet 1INVENTORS PAUL B. MARTIN, JR.

GILBERT w. SPENCER Patented Sept. 5, 1972 5 Sheets-Sheet 2 PatentedSept. 5, 1972 5 Sheets$heet 3 INVENTORS B. MARTIN JR.

' PAUL GILBE RT W. SPENCER Patented Sept. 5, 1912 I 3,688,924

5 Sheets-Sheet 4 INVENTORS PAUL B. MARTIN, JR. GILBERT w. SPENCERPatented Sept. 5, 1972 FIG. 5

5 Sheets-Sheet 5 INVENTORS PAUL B. MARTIN, JR.

GILBERT w. SPENCER SELF PROPELLED SEWAGE SLUDGE EXCAVATOR BACKGROUND OFTHE INVENTION The present invention relates in general to conveyingapparatus and more particularly to apparatus for excavating dried sewagesludge from the top of a sewage drying bed.

It is customary in many sewage plants to remove organic wastes from theliquid under treatment by filtration through a bed containing a sublayerof gravel covered by a layer of sand. The build-up of sludge on the bedreduces the filtration rate. It is common practice to periodically takea given bed off stream, allow the sludge and the bed to dry, and removethe dried sludge.

At present, the dried sludge which dries with mudlike characteristics toform irregular cakes of 1% to 3 inches in thickness is removed manuallyfrom the drying beds by workmen using corn forks to load the sludge ontoa belt conveyor which spans the beds and conveys the sludge to a truck.This manual cleaning of the bed is a slow, tedious operation. Due to thephysical labor involved and the poor working conditions, it is difficultto obtain and retain personnel to perform this work.

Another disadvantage of the prior art manual cleaning procedure is thatthe workmen walk upon and disrupt the bed. A typical drying bed whenfreshly replenished has a 6-inch layer of gravel overlayered with an8-inch layer of filtering sand. In walking upon the surface of the bedin the course of removing the dried sludge, the workmens footprintscreate variations in the thickness of the sand layer which manifestsitself in causing the bed to dry out unevenly. Thus, one area of a bedmay appear fully drained and cured while another area remains soggy. Inaccordance with the present invention, a more uniform bed is maintainedsince the necessity for workmen stepping upon the bed is obviated, and areduction in bed drying time should be obtained.

SUMMARY OF THE INVENTION It is a primary object of the present inventionto provide a fully mechanized approach for removing the sludge fromsewage drying beds.

Another major object of the present invention is to effect sludgeremoval from a drying bed with minimum disturbance of the sand layer inorder to maintain greater bed uniformity and consequently to achieve anoverall reduction in the bed drying time.

The above and other objects, features, and advantages of the inventionwill become more apparent as this description proceeds.

A presently preferred embodiment of the invention comprises an excavatorwhich isconstituted by a plurality of limited tilting double tinedscoops connected to an endless chain drive. The scoops pick up thesludge cake from the bed leaving the sand layer relatively undisturbedand transport the sludge upwardly to be discharged onto a conveyor foreventual removal from the bed area. The scoops are double tined toenable the chain conveyor to be driven in both directions so that thereis no lost time when the excavator traverses the drying bed in twodirections along parallel rows by means of a reciprocating carriagemechanism. The

carriage mechanism at the end of each row is advanced the width of theexcavator in a direction perpendicular to the row direction to ready theexcavator for its next movement across the bed.

Adjustment means are provided for providing the leading edges of thescoops with a slight downward tilt regardless of which direction thescoops are moving in order to avoid the trailing edge of the scoopheeling" or cutting through the sand as the scoop passes through thesludge pickup zone and is cocked to travel upwardly to the zone ofdischarge onto the conveyor.

Additional adjustment means are provided to elevate the scoop assemblyto clear the drying bed walls and to compensate for varying sand depthsfrom bed to bed so that the apparatus may be utilized to clean beds ofdifferent dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of apresently preferred embodiment of the invention installed in a sewagetreatment plant.

FIG. 2 is a plan view of a portion of the apparatus showing FIG. 1.

FIG. 3 is a vertical cross-sectional view taken generally on the line3-3 of FIG. 2.

FIG. 4 is a vertical cross-sectional view taken on the line 4-4 of FIG.2.

FIG. 5 is a detail view on an enlarged scale showing the position of oneof the scoops at the time of removing sludge from a drying bed.

FIG. 6 is a view similar to FIG. 5 but showing the excavator moving inthe opposite direction.

FIG. 7 is a perspective view of adouble tined scoop' utilized incarrying out the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings andmore particularly to FIG. 1, reference numeral 10 generallydesignates'an excavator in accordance with a presently preferredembodiment of the invention. The excavator is utilized to remove a driedsludge layer 12 from the top of a sewage drying bed comprising a gravelunderlayer l4 and a sand top layer 16. Low concrete walls 18 extendaround the perimeter of each bed and, as is customary, a number ofdrying beds may be arranged in rows separated from each other by one ofthe walls 18.

As will be explained more fully hereinafter, the excavator 10 removesthe sludge and transports it upwardly for discharge onto a crossconveyor 22 from which the sludge passes through chute 24 onto aconveyor 26 which is connected to a framework 28 spanning the bed. Thedischarge end of conveyor 26 which is inclined upwardly as seen in FIG.1 is intended to discharge the sludge into a truck or similar vehiclefor disposal.

The excavator 10 contains a vertically disposed endless conveyormechanism comprising a plurality of double tined scoops generallydesignated by reference numeral 30 which are connected to a pair ofendless chains 32. The chains are driven by a motor 34, a drive chain 36trained around suitable sprockets 38 and 40. The sprockets 40 rotate ashaft 42 causing rotation of conveyor drive sprockets 44 which are intoothed engagement with the chains 32 at the bottom of their path ofmovement. At the top of their path of movement the chains 32 are trainedover two spaced pairs of sprockets 46 with the sprockets of each pairbeing disposed at opposite ends of a shaft disposed within tubing 48.

Referring to FIGS. 5-7 which best illustrate the details of the scoops30, it will be seen that each scoop is comprised of a plurality ofspaced rods 50 welded to the bottom of a central wall member 52 and apair of side walls 54. This structure results in a double tinedarrangement, i.e., a scoop structure which may be utilized to removesludge from the drying beds in both directions of movement of the chains32. The scoops are attached to the conveyor chains by support arms 56which are pivotally connected to the scoops at their lower ends at pivotpoints 58 and which have upper flanges 60 secured to the chains 32. Inview of the pivot points 58, the scoops may move arcuately about thesepivot points but this movement is limited by abutment blocks 62. Twoabutment blocks are secured to each side wall 54 on opposite sides ofthe support arm 56.

FIGS. 5 and6 illustrate the purpose of the abutments 62 and alsoillustrate the scoops operating in both directions of rotation of thechains 32. In FIG. 5, the conveyor chains 32 are rotating clockwise asshown by the arrows. Each scoop 30 approaches the sludge pickup zone atthe bottom of the conveyor chain path with the lower end of the scooptilted downwardly or counterclockwise with regard to the support arm 56due to gravity. The extent of tilting is limited by the support arm 56abutting against the right-hand abutment 62. Thus, when the scoopapproaches the bottom of its path of travel and initially contacts thesludge, the

' rods 50 are tilted downwardly at a slight angle to the horizontal asshown in FIG. 5. The rods 50 which constitute the tines break into andpick up the sludge which normally is in the form of irregular cakes of1% to 3 inches thickness with minimal disturbance of the sand layer. Thedownward tilting of the leading edges of the scoop which may be in theorder of 5 or so prevents the trailing or'right-hand ends of the rods 50heeling or cutting into and disrupting the sand layer as the scooppasses through the pickup zone and commences upward vertical movementalong the endless conveyor path. It will be appreciated that with theconveyor chains moving clockwise sludge is picked up only by the rods atthe left-hand side of the scoops as seen in FIG. 5, and that when theloaded scoops move upwardly to their discharge zone, the sludge will beto a large part supported against the surface of the central wall 52.

When the conveyor chains 32 are rotating in the opposite direction,i.e., counterclockwise as shown in FIG. 6, the principle of operation isthe same but in this case the right-hand end of each scoop is tilteddownwardly around pivot point 58 with the extent of this movement beinglimited by the support arm 56 contacting the left-hand abutment 62. Inthis case it is the right-hand half of the scoops which is utilized inpicking up the sludge rather than the left-hand half as was the casewith the conveyor chains rotating clockwise as illustrated in FIG. 5.

The scoops when loaded with sludge move vertically upwardly and thenpass over sprockets 46 beneath a cover 64 as seen in FIGS. 3 and 4.During the horizontal path of movement of the chains between the pairsof sprockets 46 at which point the scoops are above the chains, thesludge falls off the scoops 30 onto the cross conveyor 22. In theillustrated embodiment conveyor 22 is an endless belt which extendsbetween a pair of fixed side walls 66 formed by channel irons supportedupon cross members of an upper excavator horizontal frame generallydesignated by reference numeral 68. The belt conveyor is driven by aright angle gear motor 70 which is connected to the shaft of a conveyordrive roller 72 via a coupling 74.

As mentioned previously, the conveyor 22 discharges the sludge through achute 24 onto a conveyor 26 attached to a framework 28, both of whichspan the drying bed. The details of conveyor 26 and framework 28 are nota material part of this invention. In fact, these devices are existingstructure in a number of sewage treatment plans and heretofore it hasbeen customary for workmen to manually shove] the sludge from the bedonto the conveyor 26 which in the illustrated embodiment is shown as abelt conveyor. The entire assembly may be moved longitudinally along thedrying bed, i.e., from left to right or vice versa as seen in FIG. 1 viawheels 76 on the bottom of framework 28 which run along tracks 78provided on top of the walls 18. a

The excavator is moved transversely of the bed 12, i.e., between thewalls 18 illustrated in FIG. I by means of a carriage assemblycomprising two pairs of double flanged wheels 80 which run on tracks 81on top of the framework 28. Each pair of wheels 80 is rigidly connectedto a shaft 82. The shafts 82 are rotatably con nected to the excavatorframe 68 by ball bearing units 84 at both ends of the shafts. As seen inFIG. 3, casters 83 which are connected to a support structure 85 for theexcavator engage the vertical portions of tracks 81 to preclude unwantedlateral movement. Similarly, a caster 87 which is connected to thevertical framework of the excavator engages a channel member 89 which issecured adjacent the bottom of the framework 28. Movement of thecarriage assembly along the tracks 81 is caused by right angle gearmotor 86. The motor 86 has a drive sprocket 88 which rotates the frontshaft 82 via chain 90 and a sprocket 92 which is rigidly connected tothe front shaft 82. In turn, drive sprocket 93 mounted on front shaft 82rotates rear shaft 95 via chain 97 and sprocket 99 to thereby affordfour-wheel drive for the carriage assembly.

The operation of the apparatus is controlled by an operator located inan operators booth 94 which has a roof 96, a seat 98, and a controlpanel 100 (FIG. 3).

In order to move the excavator 10 from one bed 12 to another, it isnecessary to elevate the lower end of the excavator above the height ofthe wall 18. This is accomplished by mounting the excavator 10 forvertical reciprocating movement relative to the vertically fixed supportstructure 85 to which are connected metal rollers 102 located inU-shaped tracks in a vertically adjustable frame 104 of the excavator.The vertical position of the excavator is regulated via an electricallyactuated hoist 106 and a chain 108 which is trained about a sprocket 110which is rotatably connected to a cross member 112 of the excavatorframe 104. At its upper end, the chain 108 is trained about a sprocket114 and terminates in a hook 116 which is connected to a ratchet wrench118 located in the operators booth 94.

While it is believed that the operation of the apparatus is apparentfrom the foregoing description, the main operational steps will bebriefly summarized. For purposes of illustration, it will be assumedthat the apparatus is in the position shown in FIG. 1 and is ready tostart another traverse across the bed 12. With the conveyors 22 and 26already in operation, the operator actuates motor 34 to drive the chains32 and scoops 30 clockwise, and then actuates motor 86 to commencemovement of the excavator along the tracks 81 on the framework 28. Whenthe excavator reaches the opposite side of the bed 12, movement of theexcavator is stopped. An electrical sensing control may be provided toprevent over-travel of the excavator as it approaches the walls 18. Theoperator now causes the entire illustrated apparatus to move to theright as seen in FIG. 1 a distance equal to the width of scoops 30. Thismovement is accomplished by a control means and a motor not shown whichcause the wheels 76 to move along the tracks 78 on top of the walls 18.Then, after the operator reverses the direction of rotation of thescoops 30 and chains 32, i.e., so that they now rotate counterclockwise,the excavator is caused to again move along the tracks 81 but now fromthe front wall 18 to the rear wall.

When it is desired to move the excavator from one bed 12 to another, forexample, to a bed on the opposite side of the rear wall 18, theexcavator is elevated within the support structure 85 by the hoistassembly to a height sufficient to clear the wall 18. Then the excavatormay be moved further along the tracks 81 onto the adjacent bed for usein removing sludge from that bed.

While a presently preferred embodiment of the invention has been shownand described with particularity, it will be appreciated that manychanges and modifications may readily suggest themselves to those ofordinary skill in the art upon being apprised of the present invention.For example, certain aspects of the invention may have utility outsideof the sewage treatment art, and other conveyor drive means equivalentto those described might be utilized. It is intended to encompass theseand all other changes and modifications which fall within the scope andspirit of the appended claims.

What is claimed is:

1. In a sewage treatment system having at least one drying bed, wallssurrounding said drying bed, a framework extending across said dryingbed, and means for moving said framework along the length of said dryingbed, the improvement comprising excavator means for removing sludgedeposited upon said drying bed, said excavator means including aplurality of interconnected spaced scoops travelling in an endless path,said scoops at the lowermost portion of said endless path being inposition to engage the sludge to be removed, drive means to move saidscoops interchangeably in both a clockwise direction and in acounterclockwise direction in said endless path, said scoops having aconfiguration to remove sludge in both directions of movement of saidscoops in said endless path, adjustment means to adjust the position ofsaid scoops at the bottom of their path of movement relative to theupper surface of said drying bed, means for reciprocating said excavatoralong said framework, and conveyor means to receive sludge discharged bysaid scoops at a discharge zone in their path of travel and to conveysaid sludge away from said excavator.

2. A system according to claim 1, wherein each scoop comprises a centralwall member, a pair of side walls at opposite ends of said central wallmember, and a plurality of elongated rod members secured to the bottomof said center wall member generally perpendicular thereto and extendingon each side of said central wall member.

3. A system according to claim 1, further comprising a pair of endlesschains, support arms pivotally connected at one end to said scoops andat the other end being rigidly connected to said endless chains, andabutment means to limit the relative pivotal movement between each scoopand its respective support arms so that regardless of the direction ofrotation of the scoops in said endless path the forward edge of thescoop is inclined downwardly at a small angle to the horizontal at thebottom of said endless path.

4. A system according to claim 1, wherein said means for reciprocatingsaid excavator along said framework comprises a wheeled carriageconnected to said excavator, tracks mounted on said framework upon whichsaid wheeled carriage reciprocates, and drive means for said wheeledcarriage.

5. A system according to claim 4, wherein said conveyor means includesan endless belt conveyor having a feed end positioned beneath a zone ofsludge discharge from said scoops, said endless belt conveyor beingconnected to said excavator and moved jointly therewith along saidframework.

6. A system according to claim 1, wherein said excavator includes avertically fixed support structure and a frame in sliding engagementwith respect to said support structure, and hoist means to elevate saidframe with respect to said support structure to enable said excavator topass along said framework over one of the walls of said drying bed.

7. An excavator comprising a plurality of interconnected spaced scoopstravelling in an endless path, drive means including a pair of endlesschains to move said scoops interchangeably in both a clockwise directionand in a counterclockwise direction in said endless path, said scoopshaving openings at two opposite sides to enable material to be conveyedto enter said scoops in both directions of movement of said scoops insaid endless path, means to vertically adjust the position of saidscoops in a pickup zone relative to the material to be conveyed, eachscoop having a pair of support arms pivotally connected thereto, saidsupport arms being rigidly connected at one end to said endless chains,and abutment means to limit the rela-- tive pivotal movement betweeneach scoop and its respective support arms so that regardless of thedirection of rotation of the scoops in said endless path the forwardedge of the scoop is inclined downwardly at a small angle to thehorizontal as each scoop enters the pickup zone.

8. Apparatus according to claim 7, wherein each scoop comprises acentral wall member, a pair of side walls at opposite ends of saidcentral wall member, and a plurality of elongated'rod members secured tothe bottom of said central wall member generally perpendicular theretoand extending on each side of said central wall member.

9. Apparatus according to claim 7, further comprising a-wheeled carriagefor moving said excavator along the material to be conveyed, and drivemeans for said wheeled carriage.

10. Apparatus according to claim 7, wherein said ex-

1. In a sewage treatment system having at least one drying bed, wallssurrounding said drying bed, a framework extending across said dryingbed, and means for moving said framework along the length of said dryingbed, the improvement comprising excavator means for removing sludgedeposited upon said drying bed, said excavator means including aplurality of interconnected spaced scoops travelling in an endless path,said scoops at the lowermost portion of said endless path being inposition to engage the sludge to be removed, drive means to move saidscoops interchangeably in both a clockwise direction and in acounterclockwise direction in said endless path, said scoops having aconfiguration to remove sludge in both directions of movement of saidscoops in said endless path, adjustment means to adjust the position ofsaid scoops at the bottom of their path of movement relative to theupper surface of said drying bed, means for reciprocating said excavatoralong said framework, and conveyor means to receive sludge discharged bysaid scoops at a discharge zone in their path of travel and to conveysaid sludge away from said excavator.
 2. A system according to claim 1,wherein each scoop comprises a central wall member, a pair of side wallsat opposite ends of said central wall member, and a plurality ofelongated rod members secured to the bottom of said center wall membergenerally perpendicular thereto and extending on each side of saidcentral wall member.
 3. A system according to claim 1, furthercomprising a pair of endless chains, support arms pivotally connected atone end to said scoops and at the other end being rigidly connected tosaid endless chains, and abutment means to limit the relative pivotalmovement between each scoop and its respective support arms so thatregardless of the direction of rotation of the scoops in said endlesspath the forward edge of the scoop is inclined downwardly at a smallangle to the horizontal at the bottom of said endless path.
 4. A systemaccording to claim 1, wherein said means for reciprocating saidexcavator along said framework comprises a wheeled carriage connected tosaid excavator, tracks mounted on said framework upon which said wheeledcarriage reciprocates, and drive means for said wheeled carriage.
 5. Asystem according to claim 4, wherein said conveyor means includes anendless belt conveyor having a feed end positioned beneath a zone ofsludge discharge from said scoops, said endless belt conveyor beingconnected to said excavator and moved jointly therewith along saidframework.
 6. A system according to claim 1, wherein said excavatorincludes a vertically fixed support structure and a frame in slidingengagement with respect to said support structure, and hoist means toelevate said frame with respect to said support structure to enable saidexcavator to pass along said framework over one of the walls of saiddrying bed.
 7. An excavator comprising a plurality of interconnectedspaced scoops travelling in an endless path, drive means including apair of endless chains to move said scoops interchangeably in both aclockwise direction and in a counterclockwise direction in said endlesspath, said scoops having openings at two opposite sides to enablematerial to be conveyed to enter said scoops in both directions ofmovement of said scoops in said endless path, means to vertically adjustthe position of said scoops in a pickup zone relative to the materIal tobe conveyed, each scoop having a pair of support arms pivotallyconnected thereto, said support arms being rigidly connected at one endto said endless chains, and abutment means to limit the relative pivotalmovement between each scoop and its respective support arms so thatregardless of the direction of rotation of the scoops in said endlesspath the forward edge of the scoop is inclined downwardly at a smallangle to the horizontal as each scoop enters the pickup zone. 8.Apparatus according to claim 7, wherein each scoop comprises a centralwall member, a pair of side walls at opposite ends of said central wallmember, and a plurality of elongated rod members secured to the bottomof said central wall member generally perpendicular thereto andextending on each side of said central wall member.
 9. Apparatusaccording to claim 7, further comprising a wheeled carriage for movingsaid excavator along the material to be conveyed, and drive means forsaid wheeled carriage.
 10. Apparatus according to claim 7, wherein saidexcavator further includes a vertically fixed support structure, a frameelevatable with respect to said support structure, and hoist means toelevate said frame relative to said support structure.